IT devices are configured so that several CPUs, memories, and control elements are mounted on a circuit board. A backplane on the rear side of a rack supplies electrical power to the circuit board and exchanges signals with the circuit board.
In recent years, high-density packaging of CPUs and memories is essential in order to process an enormous amount of data, thereby providing an improved capability. Therefore, one-hundred or more module boards, which are prepared by mounting CPUs, memories, and control elements on both sides of the module boards, are mounted on a large-size motherboard. As such being the case, the module boards have to be unmounted and remounted whenever they need to be accessed for the purpose of maintaining and servicing the CPUs and memories.
As a prior-art technology concerning the above-mentioned module boards, a heat dissipation structure and its manufacturing method are disclosed in Japanese Patent Application Laid-Open No. 2009-16605 (PTL 1). This heat dissipation structure makes it possible to eliminate the variation of a heat dissipation surface, achieve heat dissipation with high efficiency, reduce the size and weight of a device, and provide increased ease of device assembly.
Further, a prior-art technology disclosed in Japanese Patent Application Laid-Open No. 2005-223099 (PTL 2) provides a first electronic component heat transfer cover and a second electronic component heat transfer cover. The first electronic component heat transfer cover, which is shaped like an inverted dish, covers all electronic components mounted on the upside of an electronic circuit board. The second electronic component heat transfer cover, which is also shaped like an inverted dish, covers all electronic components mounted on the underside of the electronic circuit board.
Furthermore, a prior-art technology disclosed in Japanese Patent Application Laid-Open No. 2008-010768 (PTL 3) provides a circuit board that is sandwiched between a first heat sink and a second heat sink. The first heat sink is equipped with a heat pipe and attached to the upside of the circuit board. The second heat sink is attached to the underside of the circuit board.
Moreover, a prior-art technology disclosed in Japanese Patent Application Laid-Open No. 2010-080507 (PTL 4) provides a method of thermally connecting a CPU, which is a major heat source mounted on a wiring board, to one outer surface of a thermo-siphon, attaching a plurality of heat pipes to the other outer surface of the thermo-siphon, and establishing a thermal connection by attaching one end of each heat pipe to the upside of an element generating a small amount of heat.
Besides, a prior-art technology disclosed in Japanese Patent Application Laid-Open No. Hei 08 (1996)-125371 (PTL 5) provides a method of cooling heat-generating components through a metal core incorporated in an inner layer of a printed circuit board, disposing a retaining member between the printed circuit board and a guide section, thermally connecting a cooling plate to the guide section in order to transfer heat to a fluid, and securing the printed circuit board to the guide section to thermally connect the metal core in the printed circuit board to the guide section.